Image judging device and image judging method

Abstract

An image judging device for judging whether an image represented by input image data is a defocused image or not includes an evaluation value calculating unit and a judgment unit. The evaluation value calculating unit calculates a predetermined evaluation value on the basis of normalized orthogonal transform coefficients acquired from the input image data encoded by a normalized orthogonal transform. The judgment unit judges whether an image represented by the input image data is a defocused image or not on the basis of the calculated evaluation value.

1 . An image judging device for judging whether an image represented by input image data is a defocused image, the image judging device comprising:
 an evaluation value calculating unit for calculating an evaluation value on the basis of normalized orthogonal transform coefficients acquired from the input image data encoded by a normalized orthogonal transform; and   a judgment unit for judging whether an image represented by the input image data is a defocused image on the basis of the calculated evaluation value.   
   
   
       2 . The image judging device according to  claim 1 , wherein the normalized orthogonal transform is a discrete cosine transform, and
 wherein the evaluation value calculating unit calculates the evaluation value on the basis of discrete cosine transform coefficients as the normalized orthogonal transform coefficients acquired from the input image data encoded by the discrete cosine transform.   
   
   
       3 . The image judging device according to  claim 2 , wherein the evaluation value calculating unit calculates the evaluation value on the basis of the discrete cosine transform coefficients corresponding to a predetermined low frequency. 
   
   
       4 . The image judging device according to  claim 3 , wherein the evaluation value calculating unit calculates a coefficient integrated value R 1  obtained by integrating absolute values of the discrete cosine transform coefficients corresponding to a first frequency which is lowest, a coefficient integrated value R 2  obtained by integrating absolute values of the discrete cosine transform coefficients corresponding to a second frequency which is the second lowest, and a coefficient integrated value R 3  obtained by integrating absolute values of the discrete cosine transform coefficients corresponding to a third frequency which is the third lowest and calculates the predetermined evaluation value expressed by Fb=(R 1 −R 2 )/(R 2 −R 3 ) on the basis of the calculated coefficient integrated values R 1 , R 2 , and R 3 . 
   
   
       5 . The image judging device according to  claim 1 , wherein the judgment unit judges that the image represented by the input image data is a focused image when the calculated evaluation value is within a predetermined range and judges that the image represented by the input image data is a defocused image when the calculated evaluation value is not within the predetermined range. 
   
   
       6 . The image judging device according to  claim 5 , further comprising an evaluation threshold determining unit for determining evaluation threshold values defining the predetermined range,
 wherein the evaluation threshold determining unit determines the evaluation threshold values corresponding to an output size indicating a size of the image represented by the input image data and an image size indicating a resolution of the input image data, with reference to evaluation threshold information prepared in advance.   
   
   
       7 . The image judging device according to  claim 1 , further comprising a printing unit for printing an image not judged to be a defocused image by the judgment unit. 
   
   
       8 . The image judging device according to  claim 1 , wherein the evaluation value calculating unit sets one or more evaluation areas in the image represented by the input image data and calculates the predetermined evaluation value for every set evaluation area, and
 wherein the judgment unit judges that the image represented by the input image data is a defocused image when all the evaluation areas are judged as being defocused and judges that the image represented by the input image data is a focused image when one of the evaluation areas is judged as being focused, on the basis of the evaluation value calculated for every evaluation area.   
   
   
       9 . An image judging method of judging whether an image represented by input image data is a defocused image or not, the image judging method comprising:
 (a) calculating a predetermined evaluation value on the basis of normalized orthogonal transform coefficients acquired from the input image data encoded by a normalized orthogonal transform; and   (b) judging whether an image represented by the input image data is a defocused image or not on the basis of the calculated evaluation value.   
   
   
       10 . A program product for judging whether an image represented by input image data is a defocused image or not, the computer program allowing a computer to execute:
 (a) a function of calculating a predetermined evaluation value on the basis of normalized orthogonal transform coefficients acquired from the input image data encoded by a normalized orthogonal transform; and   (b) a function of judging whether an image represented by the input image data is a defocused image or not on the basis of the calculated evaluation value.   
   
   
       11 . A computer-readable recording medium having the computer program according to  claim 10  recorded thereon.